I'm currently getting fever upto 99.4 irregualrly. some medical tests are negative. what can it be, what should i do?

Low grade temp: For most, a fever is greater than 100.4. However everyone is unique -from the nose we have to the body temp we keep. I'm not sure 99.4 is really significant. Do you have any other symptoms to go on? If your testing so far has been negative, then I'm not worried about you. Maybe there's something in your routine you can change/improve. Try 8 hrs sleep? Drink more water? Eat more fruit. Feel better.